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Biogeochemical blindspots along the lower Amazon River continuum: from land to the atmosphere and ocean

Grant number: 18/18491-4
Support type:Research Projects - SPEC Program
Duration: May 01, 2019 - April 30, 2023
Field of knowledge:Physical Sciences and Mathematics - Geosciences
Principal Investigator:Jeffrey Edward Richey
Grantee:Jeffrey Edward Richey
Home Institution: Centro de Energia Nuclear na Agricultura (CENA). Universidade de São Paulo (USP). Piracicaba , SP, Brazil
Co-Principal Investigators:Maria Victoria Ramos Ballester
Assoc. researchers: Alan Cavalcanti da Cunha ; Henrique Oliveira Sawakuchi ; Maria de Lourdes Cavalcanti Barros ; Milton Kampel ; Nicholas Ward ; Paulo Cesar Colonna Rosman ; Richard G Keil ; Vania Neu

Abstract

The research objective is to examine, at different scales, the processes that govern the advection and reaction of carbon in the lowest reach of the Amazon River and along the near-shore coastline of the Western Tropical Atlantic Ocean. The mainstem of the river is a large supplier of carbon dioxide (CO2) to the atmosphere, most of which is sourced as organic carbon from the surrounding landscape and subsequently remineralized in river. The component of the river system that is least well understood is the lower tidal reach, which consists of two main channels across from Macapá down 150 km to the ocean. While tidal forcing does not result in salt intrusion, riverine flow in this reach can be reversed, and complex interactions occur between the river channels and the fringe areas, making the study of this component of the world's largest river a significant logistical challenge. Through an ambitious field study, the project aims to understand the large-scale drivers (e.g. hydrodynamics, areal extent, metabolism) that create the spatial and temporal variability in carbon remineralization and CO2 fluxes in the lower river. This will be addressed using a combination of fieldwork, remote sensing and modeling. In addition, the types of organic matter that are degraded, the microorganisms and consortia that remineralize, and the metabolic pathways (aerobic, anaerobic) that lead to the large production of CO2 will be evaluated using a combination of organic geochemical and molecular biological (proteomic) tools. The proposed work will provide in situ observations in a previously unstudied region of high global importance, experimentation focused on unraveling the influence of physical factors (e.g. tides, current velocity, and mixing) on biological processes, spatial and temporal variability of CO2 fluxes by remote sensing, and modeling tools capable of predicting the sensitivity of Net Ecosystem Exchange (NEE). (AU)